Suunto D6 in full panic mode (part II)

Yesterday I told you about a dive on Doodles, a reef in southern Mozambique, during our trip to Ponta do Ouro last month. Doodles has a maximum depth of about 14 metres. After forty five minutes’ dive time, my Suunto D6 began to register extreme depths (89 metres maximum), and to give various instructions about decompression ceilings and times, accompanied by strident warnings about exceeding my PPO2.

Suunto D6 after missed decompression
Suunto D6 after missed decompression

While annoying and potentially dangerous to lose the services of my dive computer mid-dive, it was also an excellent learning opportunity. Because I usually try quite hard to be safe and not to upset my computer, and dive within the conservative, recreational limits that I am trained for, I never get to see any of this behaviour from the instrument. (Fortunately the dive was shallow and I still had plenty of no-decompression time left so it was far from an emergency situation.)

After the dive, I soaked the computer in warm fresh water, and it gradually came out of dive mode over a period of about ninety minutes. During the course of this simulated ascent, the required decompression times and depths calculated by the algorithm were not adhered to, so the computer entered an error mode, which, according to the manual, indicates that “the risk of DCI has greatly increased.” (In fact, from all the beeping and flashing, I suspect the computer thought I was dead or close to it.) This error mode does two things: it disables the dive planning capabilities of the computer, and it locks you out of dive mode for 48 hours.

The D6 in gauge mode
The D6 in gauge mode

I had never gotten the computer into this state before, so I was keen to see how it behaved when I took it on a dive in error mode. You can see in the photo above that I am wearing Tony’s Mares Nemo Wide (aka the flatscreen TV) to give me actual information about my no-decompression time, depth and dive time, but I took my D6 along for the ride. It is in gauge mode; this means it gives you only measurements, and is the setting a free diver might use.

The measurements available in gauge mode are: depth (18.4 metres in the photo above), the maximum depth you’ve been to on this dive (19.9 metres), an elapsed dive time (17 minutes), and water temperature (not shown) but it refuses to calculate a no-decompression limit for you. This would usually appear where the Er appears in the picture above.

Depth profile (with warnings)
Depth profile (with warnings)

For your enjoyment, here’s another screen shot of the dive profile from MacDive, with the warnings expanded. Click on the image to see it full size. It is clear that the first warning beeps I heard during the dive were because of elevated PPO2 levels. At 89 metres the device immediately put me in deco, and then as it “ascended” fairly rapidly, it gave a warning about oxygen toxicity (OLF or oxygen limit fraction as used in the Suunto algorithm) and an ascent rate warning. On the right, at about 10 metres, a warning is given that the depth is still below the required level to complete the decompression.

All the green circular icons appearing around the middle of my dive, where the computer thought I was at 35 metres, indicate that the computer registered that I surfaced, but not for long enough to show on the dive profile. Weird!

My D6 remained angry for 48 hours after the dive at Doodles; by this time, we had finished our diving for the week. I’m not sure whether the problem with the pressure sensor is a permanent one (requiring repairs, a service or a new dive computer), or whether it was just dirty or stuck and will have resolved itself next time I dive with the instrument. I’ll be wearing a spare dive computer when I do, just in case.


Yesterday’s post perhaps left us all feeling a bit deflated. So let’s get to the good stuff.

How is a boat re-pontooned?

First, the glued attachment strips are heated and removed and the pontoons, still intact, are also removed. You can see just how little boat there is once they are off.

Step two is to open each section of the tube, separate the compartments and use them as templates to cut out the new ones. A huge cutting table is used as well as a whole range of markers, steel rulers and heat guns.

Pontooning in progress
Pontooning in progress

The company we used, Ark Inflatables, don’t glue the seams – they weld them instead. So the tubes are all welded together individually and assembled section by section, and then on they go. The pontoons are held to the hull by a series of attaching strips and are also glued to the hull where they meet. Once they are on and secured, they are ready for the third step: accessories.

The various options of what accessories to add require some special consideration. Ark are extremely flexible and helpful when it come to weird and wonderful customer requests. Depending on the use of the boat there are a wide range of options.

We use the jetties in Simon’s Town, Hout Bay and occasionally at Miller’s Point or Oceana Power Boat Club near the Waterfront. Some of these jetties are poorly configured for smaller boats, so pontoon damage and abrasions can be a huge problem. They are also primarily black rubber tyres or bollards to tie up against, and these mark the pontoons. To solve that problem we added four rows of rubbing trim.

We anchor at some of our dive sites and in order to set and retrieve an anchor without damaging the bow we added a really wide rubber buffer and rope channel.

Front channel for anchor ropes
Front channel for anchor ropes

Getting back into a dive boat can be challenging for some, so to ease that issue we added three lines to each pontoon section: a grab line to hold once you have surfaced and reached the boat, a top taut line to yank yourself up on, and a third line, to grab as you exit the water, on the inner wall of the pontoon. This line also serves as a secure place to place fins whilst the boat is underway.

Having spent most of my life around boats I know that anything you have onboard, if it’s not attached it’s going to the bottom, so there are around 25 D-rings on the boat for clipping off anything that you want to keep. An old issue with the boat before was the attachment of the bow rail: it would pop out if a diver was hanging on it, this now has a double set of attachments.

The top of the pontoons take a beating from the sun, people stepping on and off, and of course weight belts and cylinder boots. To solve this we added a second skin down the entire length of the pontoon and these will now be ”wear strips” that can be replaced if the are damaged.

Protective pontoon cover and ropes in progress
Protective pontoon cover and ropes in progress

Lastly, to maintain the correct pressure when the day time temperatures  exceeed 30 degrees and the night time temperatures plummet, this coupled with a sudden cooling once you hit the water, we had them install an over pressure valve on each section, meaning it can never be pumped too hard and if left in the baking sun the excess pressure will bleed off.

Overall, I think it was a job really well done and would recommend Ark to any rubber duck owner wanting to repair their boat. The boat looks a little more ‘”industrial” than it did before, but the reality is it has a task to perform and must be able to do so faultlessly. Asthetics are secondary, but we feel the boat looks rugged, tough and ready to work. Oh, and did I mention… cool!

Maintaining a boat trailer

Having a boat that you transport by trailer to and from the ocean, as opposed to having a permanent mooring in your local yacht basin, adds a different element of maintenance to your plans.

For example a  boat on a permanent mooring has different requirements for cathodic protection, requires an anti-fouling coat of paint on the hull, and will need to be removed at least once a year for inspection, cleaning, and so on. Fresh water flushing of the cooling system doesn’t happen and the boat needs to be checked frequently for leaks, mooring line chafe, and so on. The plus side is you can step on the boat in the morning and be ready to head out to sea in a few minutes.

A boat that you haul to and from the ocean does not need a fancy hull paint, the standard engine protection in the form of sacrificial anode is more than adequate, and you get to wash the boat and flush the cooling system in your own garden. Hull inspection, running maintenance and the like is easily taken care of while the boat sits on the trailer in your driveway.

Rim looking ropy
Rim looking ropy

The trailer and its requirements that are often neglected, however. Not everyone neglects the trailer, but it is easy to overlook some of the basic items and then end up with an excruciating problem. I have had such a problem: on one occasion I put off changing the wheel bearings for a little longer than I should have, and on the day I decided to change them I had a failure on the way home. The bearing disintegrated, the wheel came off, wrecked the fender and left me stranded by the side of the road. It’s not fun. The potential for disaster is high and should the wayward wheel hit and injure someone you could face prosecution.

Rusty rim
Rusty rim

The moral of the story is check the wheel bearings frequently, and change them as soon as they feel or sound rough or there is excessive free play. Some advocate stripping them, washing them and repacking with fresh grease every month or two, and some prefer to fit a ”bearing buddy”. This can help diagnose the conditions, i.e. if the grease inside the cover goes white there has been water in it, and if it goes black it is tired and needs changing.

Having settled into an excessive routine of checking the bearings I noticed that the wheel rims were showing a lot more rust than I was comfortable with. I took them of for a clean up and repaint but discover that some of the pitmarks were so deep they were possibly just too risky. It was time to replace them.

Fortunately the option of galvanised rims is available and the cost is not too prohibitive, so that’s what we fitted. They should last longer than rims that aren’t galvanised, and will fight off the rust a bit better.

New galvanised rims
New galvanised rims

Newsletter: Best weekend weather

Hi divers

Weekend plans

We will launch tomorrow at 8.00 and 10.30 am to go to Roman Rock and to visit the sevengill cowsharks at Shark Alley.

On Sunday we will launch at 9.30 and 12.00, to visit Photographer’s Reef and the Ark Rock wrecks.

Please remember your MPA permits.

The forecast for the weekend is by far the best I can recall seeing in a while. No wild winds, no massive swells and the water is currently warm. Day time highs are under 24 degrees so the algae should stay away. I have quite a lot of students to dive this weekend so will not have too much extra capacity.

Sea fans at Roman Rock
Sea fans at Roman Rock


There is a DAN Day  taking place on Saturday 17 May in Cape Town that looks to be very interesting. Talks include “Finding the lost diver” and “A Risk-Based Approach to Diving Operation Management”, as well as a tour of the Unique Hydra facility (which is where Andre works). If you want me to forward you the full email with details, let me know. Space is limited – sign up here.

Stripping an outboard
Stripping an outboard

French naval fleet

There are a few French naval ships, including an aircraft carrier, in Table Bay at the moment. They are supposedly open to the public for viewing but there seem to be endless complaints on the local radio stations about this not happening. Never mind, they leave on Tuesday and I will plan to launch early from OPBC to get a few pictures as they leave the Waterfront. Text me if you want to join me.


Tony Lindeque
076 817 1099

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Boat maintenance

The slimy underbelly of our boat deck
The slimy underbelly of our boat deck

Mid September, the bilge pump below the deck of our boat became erratic so I lifted one of the deck plates to take a look. Turns out it was a really good idea as the hydraulic hoses for the power steering were rubbing against a bulkhead, and would have leaked sooner or later.

Whilst the area was open I decided to replace the fuel lines from the tank to the filter, and secure the control cables, wiring looms etc as they could also end up being chafed if they floated around loose for too long.  The last time I had this panel out was about 18 months ago when I installed the Lowrance Sonar and GPS units. In this time you can see how the fuel lines had become covered with an algae that was really slimy and would most likely have damaged the fuel lines if left unchecked.

I also replaced the wiring to the existing bilge pump and installed a second one as a back-up. The area is now clean, no loose cables or looms and ready to be closed up again.

All done!
All done!

Dive gear maintenance: Wrist mount gauges

I have a range of different wrist mount gauges as I teach a range of courses. Whether it’s a compass, dive computer, or timing device the same rules apply when it comes to maintenance.

They must all be soaked in warm fresh water after a dive.


The bevel on the compass must be rotated several times in both directions whilst in the warm water. This prevents salt from building up underneath it.

Dive computers

Dive computers must have the buttons depressed several times while swirling the instrument in the warm water. This will ensure no salt crystals can build up behind the buttons. I have a Suunto Mosquito that has done over 1000 dives and has never given me a day’s trouble whereas many people have had button trouble with these units. If you have delicate water contacts brushing them with a soft toothbrush keeps them clear of build up.

I also take a soft cloth and wipe silicone over everything, pour it in behind the buttons and then wipe it all off with a clean cloth.

Dive computer in action
Dive computer in action

Dive gear maintenance: Cameras

Everyone I know has a different theory on what works for their cameras and funnily enough often very different and conflicting opinions work for different people. This is what I do…

Before you think “Wow, how clever!” please note that over the years I have, on arrival at the bottom, discovered the following:

  • no camera in the housing
  • no memory stick in the camera
  • memory card full
  • no batteries in the camera
  • flat batteries in the camera
  • more water in the housing than out of it

These things happen, but with proper care and planning you simply reduce the odds of a mistake.

Camera and housing
Camera and housing

Before a dive

Before a dive I assemble the unit by inserting fresh batteries and a formatted memory card. I use a lens pencil to gently rub the glass inside the housing and outside the housing using the soft rubber pad.

I then remove the O ring, wash it gently in shampoo or mild soap and allow it to dry. This is a good time to meticulously clean the groove on the housing with a soft lint free cloth so its ready to accept the O ring.

I then place a small blob of silicone grease in the palm of my hand and gently massage the O ring through the grease making sure it is all covered in a thin film of grease. I then fit it to the housing. Close the camera NOW as this is the time it will collect dust and other particles.

Turn it on at the surface, then go diving!

After a dive

After a dive, soak the camera housing with the camera inside (this makes the housing negatively buoyant so it doesn’t float on the surface). Keep the fresh water lukewarm and press all the buttons several times whilst the housing is submerged, especially the buttons you don’t often use underwater. My video camera has a filter and a wide angle lens and I remove these items from the housing and soak them all individually, carefully brushing the threads with a soft toothbrush.

Take the unit out of the water and try to lie it on a towel with the buttons facing down so the water will drain from the small recess in which the buttons, seals and springs are housed. This assists in preventing build-up in these small spaces that are hard to clean. If you are going to open the housing before it is dry avoid water entering the housing and try not touch the camera with wet hands.

I prefer to remove the O ring seal, twist it gently into a figure of eight and place it in the housing and then close it for storage. I feel this allows the seal to maintain its integrity as opposed to being squeezed during storage. I don’t like to leave the housing open but do prefer to store the camera in a sealed container in a cool, dark, dry place.

Dumb diving: How to drown a video light

Electronic innards
Electronic innards

A while back I mentioned the term “dumb diving”. For those that missed it, it is the term used when doing something whilst diving that is so stupid you can’t believe you were capable of it.

Well, my latest dumb dive was to Photographer’s Reef, with my video camera. I did a nice backward roll off the boat, and descended to the sea floor – only to find the batteries and cover of my video light had reached the sand before me. That’s DUMB!! Anyway, fortunately the batteries were out by the time the electronics got wet. This together with the fact that I surfaced immediately and gave the light to the boat skipper, who sprayed it with Q20, seem to have saved the light.

The video light taken apart
The video light taken apart

When I got home I stripped it completely, rinsed it in warm water, sprayed it with Q20 and then let it dry. After a few hours I cleaned it carefully with ear buds and assembled it. Hey presto – it worked. The batteries spent the dive in my pocket (DUMB!) and although they charged up again and still work the rust has started to grip them and I doubt they will last long. You can see the corrosion around the battery posts. The light is now back together again and working well. I was lucky this time as very few electronic items take well to exposed submersion.

Corroded batteries
Corroded batteries

I have also drowned other items. I have a Sony point and shoot camera with housing. The housing has leaked twice in the 10 years that I have had it. I think it is a good idea to replace the seal (o-ring) according to the manufacturer’s specification, usually a year, otherwise it will fail sooner or later. Sadly with digital cameras they upgrade and change shape faster than you can blink and it is not always as easy as replacing the camera and using the old housing. In both instances I have found a used camera on-line, as the new version did not fit the housing.

If you have had a DUMB DIVE post the details in the comments block.

Some of my examples:

  • Forgetting to put the memory stick in the camera
  • Forgetting to put batteries in the camera
  • Negative entry with a snorkel
  • Car remote in your pocket
  • Forgetting to remove the camera lens cover before putting it inside the housing (this is a Clare example)

Suunto D6 dive computer

I’ve been using the Suunto D6 dive computer for about eight months now, having finally got my grubby paws on it just after returning from our last trip to Sodwana. I think it’s about time I write a little review of it, because Suunto have just released the D6i and before you know it my computer will be a museum relic.

Specifications and appearance

The D6 is near the upper end of the range of Suunto dive computers – the model I have will now set you back in the region of R10,000 and there are several cheaper but no less effective offerings. The USB interface cable that will enable your dive computer to talk to your computer will set you back up to a further R1,500 – although this item is frequently advertised on special by Suunto stockists and occasionally as a special bundled with the dive computer, so keep your eyes open. It’s far more usual, however, to have to buy this innocuous-looking cable separately, and gasp at the price.

You can choose an elastomer strap or a metal strap (for about R2,000 more). Although the metal strap looks really cool, it’s not really practical if you dive in varying water temperatures and change the amount of neoprene on your wrist frequently. The computer functions as a dress watch if you want to use it as one – it displays the time constantly when not in dive or memory mode – but it weighs more than a slab of chocolate (130g) and is far too large for the average lady’s wrist, so I don’t use it for this purpose except when travelling (to deny the baggage handlers at OR Tambo Airport the privilege of stealing it).

The computer has a four button interface that I find very intuitive, and I could figure it out to a large degree without reading the manual. That said, if you buy a dive computer, YOU MUST READ THE MANUAL! Don’t be a fool – you want to know EXACTLY why the thing is beeping at you, what it looks like when you go into deco, and be very sure (as one clown – who was buddied with us once because he didn’t know anyone on the boat – wasn’t) whether the “3” you see on the screen indicates a time in minutes, your current depth, or the number of brain cells you have. Read the manual!

Air integration and the D6i

The D6 has actually been replaced by the D6i, which is functionally identical but has more internal memory, and is capable of air integration with an optional (heart-stoppingly expensive) dongle that you attach to your cylinder and reads remaining air. The computer will then give you an estimate of remaing dive time based on air consumption to date. I have no interest in this (at the time I bought the D6, air integration was the main distinguishing feature from the D9) – I’d use a pressure gauge regardless, and wouldn’t feel comfortable trusting what I see as an physical, analogue process (displaying the air remaining in my cylinder) to a potentially failure-prone piece of electronics.

I know I may sound like a luddite here, but an experience Tony had on the boat a few months ago confirmed my reservations. Another instructor’s student had an air integrated computer and no pressure gauge (why bother with redundancy?). The air integration with the computer wouldn’t work, but they only discovered this on the boat when they were parked over the dive site, and – after toying with the idea of cancelling the dive, and then swapping kit so the instructor, who should have an excellent feel for his air consumption, had the set up with no pressure gauge – did a very short dive. As a mathematician I can see that having snapshots of your remaining air at 20 second intervals to look at in the dive manager software might be appealing though…

Decompression algorithm

The D6 uses the Suunto Deep Stop RGBM (Reduced Gradient Bubble Model), and allows for continuous decompression as you ascend (instead of forcing you to do stops at particular depths). It also allows you to complete your safety stops at depth – something I haven’t experimented with much, but will be using next time we dive the Lusitania. The computer recommends a safety stop once you exceed 10 metres on a dive, and if you violate the recommended ascent rate it will advise a mandatory safety stop between 3 and 6 metres. I tried to photograph the D6 during a dive where I’d switched on deep stops, but there was a 20 metre layer of green plankton blocking out the light from above, and my flash kept reflecting off the screen protector. Hence the dubious results you see here. I have 28 minutes of no-decompression time remaining, dive time is 11 minutes, depth is 20.9 metres, and my first deep stop will be at 13 metres. Maximum depth (bottom left) so far has been 23.8 metres.

Suunto D6 during a dive - first deep stop is due at 13 metres
Suunto D6 during a dive – first deep stop is due at 13 metres

You’re most likely aware of this, but a dive computer does not measure anything that is going on in your body with respect to dissolved gases. Dive computers use mathematical models – based on the original dive tables, only more sophisticated – that approximate, for the average person, how much nitrogen has gone into solution in the body’s tissues, and how fast it is being released, based on your dive profile. They measure depth temperature, and time, that’s all. For this reason many dive computers, including the D6, have an option for you to set a more conservative calculation algorithm if you’re at higher risk of DCS – for reasons of increased age, high body fat percentage, or any of the other DCS-predisposing risk factors. You can also adjust the partial pressure settings up and down if you so desire, but anything higher than 1.4 bar (ata) strikes me as reckless.

Nitrox and no-fly time

It goes without saying that the D6 is Nitrox capable, and it’s very straightforward to set the Nitrox mix. After one dive on Nitrox, the option to do a repetitive air dive disappears, and you have to manually set the oxygen percentage of your mix back down to 21%. I think this is to force you to think about what gas is in your cylinder. The D6 also handles switching to a richer mix for decompression, and this optional second mix may be set through the same menu system as the primary nitrox mix.

The D6, again like most dive computers, gives a no-fly time after you’re done with diving for the day. This time is usually well under 18 hours, but you’d do well to follow DAN guidelines for flying after diving (usually 18 hours after your last dive) and not bank on the reading given by your computer. Do not be like Gerard, who shall remain nameless, and mistake the time display on your computer for the no-fly time. After a dive on the Aster that ended at about 3.30pm, he announced that his no-fly time was “fifteen hours and twenty nine minutes.” A few minutes later, to his puzzlement, it was “fifteen hours and thirty four minutes!”

Dive Manager software

The Suunto dive manager software, that allows you to examine the details of your dives on your computer screen at home, is not compatible with Apple Macs, so I had to find another solution. I’ll review the software I do use, MacDive, in a separate post. Apparently from “fall 2011”, whenever that rolls (rolled) around, the Suunto software – DM4 – will also be compatible with Apple computers. I’ll test it when I get a chance, and let you know what it’s like… As is apparently wildly popular these days, one can also share one’s sporting activities on the Suunto Movescount site via an automatic link-up from within the software interface. And, no doubt, publish them to facebook.

Electronic compass

Suunto D6 with elastomer strap (right) and titanium strap (left)
Suunto D6 with elastomer strap (right) and titanium strap (left)

One of the major appeals for me of the D6 – and I think the feature that bumps its price up so much higher than the D4 – was the integrated electronic compass, which can be accessed at (almost) any time by holding down the top left (Select) button. In the picture at right, the D6 with the elastomer strap is on the compass display (the one on the right is in the memory log display mode which can’t be accessed during a dive). If you’re not on a dive when you use the compass, obviously the depth and dive time won’t show.

The D6i has updated the compass to allow accurate readings when your wrist is tilted; the old D6 (the one I have) is not as tolerant and you’ll need to keep your arm level as with a standard dive compass. Unfortunately the D6 doesn’t record the compass heading along with the temperature, depth and other dive statistics during the dive – or, if it does, the download software I use doesn’t access it. I suspect the former is true, since I installed Suunto’s own dive manager software on Tony’s PC to check, and there was no sign of compass headings. Boo.

What’s in the box

In the box was the computer, a strap extender, the instruction manual, a disc with the Windows-compatible dive manager software on it, and two or three scratch guards which are trimmed to fit the D6’s screen. I’ve done close to 70 dives with my D6 so far, and the scratch guard is scratched and still doing its job well. Tony’s computer, the Mares Nemo Wide, is protected with some cheap cellphone screen protectors we got from Look ‘n Listen. You can buy a generic size, and then trim it down to fit your phone (or dive computer, as the case may be). We didn’t expect this makeshift scratch guard – which is NOT designed for regular immersion in salt water – to last beyond five or ten dives, but over 100 dives and it’s going strong. I think I paid R60 for the pack of screen protector stickers, and we’ll get nine Nemo Wide-sized ones out of the package.

Buying it

Continuing with the subject of good value, one more tip for the bargain hunters. I actually bought my D6 from Cape Union Mart. They stock Suunto sports watches, and were able to order me a D6 from Suunto in Finland. I had to wait six weeks for it to arrive, and it cost R8,700. What made the deal very sweet was that by buying it on my Discovery Card which gives me a 20% discount at Cape Union Mart (thanks to my years in the Vitality program and points status), the computer ended up costing just under R7,000. I paid a further R1,200 for the download cable (I got that at a dive centre). If you have a few weeks before you need the computer, or are prepared to wait in exchange for some savings, it’s worth getting a quote from Cape Union Mart as to what they’ll charge you. If you’ve got a Discovery Card it’s a no-brainer. Email them via the website for a quotation, and they’ll tell you to print that and take it to your nearest Cape Union Mart to place the order. I had to pay a 50% deposit.

Update (late 2012): Based on feedback from other divers who have shopped for Suunto computers lately, it seems that Cape Union Mart isn’t doing this any more, unfortunately – but it’s worth asking anyway!

Maintaining it

Finally – if you have a dive computer and live in Cape Town, take it to Orca in Claremont to get the battery changed when necessary, and ask for Chris the “worship manager” (that’s autocorrect gone wild on “workshop manager”) to do it for you. Tony’s students have had baaaaad experiences (a hair across the seal, anyone?!) at other locations. There’s usually not much you can do if the service centre doesn’t seal the computer properly and it floods – your only recourse will possibly be to your insurance company.